Step 1
Lift and remove your toilet tank lid to access the interior plumbing. Locate the fill valve which connects to a large round float and which turns the flow of water on and off as the bowl is flushed.
Step 2
Flush the bowl and listen as the water rises back to its reserve level. If you notice a whining sound as the water rises near the full mark, your toilet may have a defective ballcock valve, a piece of outdated toilet technology prone to such noisemaking. The slowly closing valve causes water to squeeze through a shrinking opening, which produces the noise. Change your ballcock valve for a more modern valve that will remain in the fully open position until the water has reached its target mark, then turn off completely in one action.
Step 3
Check that the wall-mounted water supply shutoff valve is completely open, if you hear noise throughout the tank refill process. If it is wide open, check the plastic tube which runs between the tank fill valve and the vertical plastic tube or overflow pipe. Water should be running smoothly, with a good amount of force into the overflow pipe as the tank fills. If the stream is weak or interrupted in any way, manually rerun the plastic tubing so the flow is improved. If this does not eliminate the noise, a new fill valve may be required.
Step 4
Check the plumbing system vent pipe located on your roof, if noises are coming from your sink or bathtub drains when the toilet is flushed. Use a small flashlight and rope to inspect the vent shaft for blockages, then use your garden hose to flush them out. A blockage in your vent pipe often results when something large falls down your drain and can result in all manner of noises coming from your sewer pipes.
Step 5
Clear your water supply system of air, if you hear a loud banging coming from your pipes when the toilet is flushed. Locate and close the water main completely. Open every faucet and flush every toilet in your home; leave them open for about 15 minutes. Shut the water supply valve for all the toilets in your home, then open the water main valve and let the water flow from every faucet for a few moments. Shut off your faucets, then open each toilet water supply valve and test flush each toilet. The hammer sounds due trapped air should be gone.